Currently the cogeneration of energy at thermoelectric of sucroenergetics plants has gained a lot of credibility, once the biomass is burned in boilers that produce steam, replacing non-renewable fuel sources, such as natural gas and coal. The process of cogeneration of electricity through biomass burning has been one of the great products of sucroenergetics plants, but efficiency (ratio of kg-steam/MW) of the systems is the main objective of the process. Conventional procedures of condensation of turbine exhaust steam has a relatively high energy consumption when comparing with the system required as inventive herein may be attributed to the fact that modern systems are basically composed of a hull/cooled pipe condenser for recirculated water in a cooling tower.
The cogeneration of power, besides supplying the power supply of the plant itself, it generates surpluses that are sold, making it a profitable product for sucroenergetics plants. This process begins with the burning of biomass in boilers of high-pressure steam that is directed to the turbines, this steam moves the solitary rotors of the axle and at the end of the axle there is a generator that converts mechanical energy into electricity. The steam that comes off the boiler and is injected into the turbine has high pressure in overheating conditions, in this form the steam moves a set of rotors in series, having its pressure and temperature reduced until the turbine exhaust. Ideally to take advantage of the vapor pressure energy in the turbine it is necessary to reduce the pressure to the absolute vacuum thereby achieving the maximum yield of the process. This is only possible with the use of capacitors in the turbine exhaust steam and ejector system.
A need of the steam cycle is in the treated water recovery (steam condensate) this process generates a cost and a long worktime at thermoelectric plants. Because of these factors there is a need to condense the vapors to feed back with treated water the boilers that produce driving steam (high pressure steam). The required system integrates this recycling of condensed water in the evaporative condenser with the water being supplied to the boiler, keeping the principle of the reuse of treated water.
The energy consumption of the conventional system of exhaust steam condensation that uses a hull/tube condenser and cooling towers exceeds by 70% the system required in this document. Since there is a need in this process to condense the steam, in Brazil and in other countries there have been the development of cooling tower associated with a condenser hull-tube, but this process generates a high consumption of energy to move the cooling water of the hull/tube condenser and from the cooling tower.
In low temperature countries it is used the dry condensers (“air coolers”) composes of a hull/tube condenser associated to a dry cooling tower to condensate the turbine exhaust steam, in this case the power used in the condensation is directly linked to the consumption of energy by the heat exhaust. While this cooling technology apparently demands low power consumption it has a larger physical structure and it inhibits the installation of such systems in tropical countries when compared to the system described herein.
The evaporative condenser used to condense the vapor and generate vacuum in the required turbine, takes advantage of the latent heat of evaporation of water in the environment and through the air movement over the wet tube bundles promote the effect of “wet bulb temperature” cooling the tubular capacitor. The wet bulb temperature is the lowest temperature that can be reached only by the evaporation of water in the environment. It is the temperature that you feel when your skin is wet and is exposed to moving air.
The search carried out in patent banks required to present patented documents of different cooling systems of turbine condensation exhaust steam of thermoelectric.
The North American patent document U.S. Pat. No. 3,831,667 entitled COMBINATION WET AND DRY COOLING SYSTEM FOR A STEAM TURBINE discloses a cooling system that combines wet and dry action for an axial flow steam turbine, with a portion of exhaust steam of the turbine being condensed by cooling water that circulates through a hull/tube condenser cooled by a cooling tower; and having another portion of the exhaust steam condensed by cooling liquid circulated in a tube heat exchanger with fins, in which heat from the cooling liquid is transferred to the air and the cooling liquid is passed through the tubes extended through the condenser, or the cooling liquid is sprayed directly at the condenser to provide a mixture of condensation, thereby the refrigeration system with water cooling towers is smaller than dry cooling towers.
Another North American patent document U.S. Pat. No. 4,156,349 titled DRY COOLING POWER PLANT SYSTEM discloses a system for thermoelectric plants that combine the action of a condenser or cooling tower of air refrigeration (dry). Although this system is used to condense the thermoelectric turbine exhaust steam it presents an entirely different inventive concept of the system as compared to system presented herein this document.
The North American patent document U.S. Pat. No. 3,881,548 titled MULTI-TEMPERATURE CIRCULATING WATER G SYSTEM FOR A STEAM TURBINE reveals a condensing system that uses a cooling tower in multiple stages to provide multi-temperature of the water circulation for one or more condensers, and thus allowing a greater heat transfer in the cooling tower for condensing of the exhaust steam.
The Chinese patent document CN203177688 (U) titled EFFICIENT WATER RING VACUUM PUMP SYSTEM FOR CONDENSING STEAM TURBINE UNIT reveals a utility model of a vacuum condensing system in order to improve the mechanical efficiency of the steam turbine. The vacuum condensing system is composed of a boiler, a steam condensing turbine, a generator, a steam condenser, an improved absorption heat pump, a cooling tower, a low temperature heating device, an exhaust heat collector and a vacuum pump. Even though this invention presents a vacuum condensation by positioning equipment without series and sequence as an innovation, the power used to power the cooling towers, vacuum pump and the entire system is significantly greater than the power consumed by the herein presented system.
The Chinese patent document CN202250270 (U) titled STEAM TURBINE CONDENSING SYSTEM discloses a utility model of a system for condensing exhaust steam of a condensation turbine, which has a compressor, a heater, an expansion relief, and a steam condenser.
The patent document WO 2011067619 titled HYBRID COOLING SYSTEM discloses a hybrid cooling system for condensing the exhaust steam of a steam turbine that reveals a cooling system of the dry cooling circuit, a unit of air cooled by dry air that performs the heat dissipation of the cooling water. According to the invention, the cooling water circulating in the dry refrigeration circuit is separated from the cooling water that circulates in the moist cooling circuit, and the dry and wet cooling circuits are connected to a common condenser.
The North American patent document U.S. Pat. No. 6,233,941 titled CONDENSATION SYSTEM reveals a condensing system for condensing turbine exhaust steam that uses together a surface condenser and a direct contact condenser. The system combines a hybrid cooling tower that combines the wet-dry action. According to the invention it has the advantages that the manufacturing costs of the installation condenser be reduced by reducing the heating tube surface, the power of the turbine is increased by reducing the condenser pressure caused by the hybrid cooling tower.
The Korean patent document KR20100057573 titled THE CONDENSING SYSTEM FOR STEAM TURBINE USING REFRIGERANT EVAPORATION HEAT discloses a system for condensing the turbine exhaust steam that has a steam condenser in which the cooling liquid circulates, a condenser that condenses the refrigerant gas generated in the vapor condenser, a cooling fluid tank, the condensed refrigerant liquid in the condenser and a pump. A cooling circuit of the cooling liquid is formed by a steam condenser, a cooling fluid tank and pumps that supply fluid through tubes connected in a closed circuit.
Another North American patent document US 2014034273 titled EPAVORATIVE CONDENSER RADIATING MODULE FOR STEAM EXHAUST OF A STEAM TURBINE discloses an evaporative condenser for condensing turbine exhaust steam that has a bundle of tubes and steam chambers.
As presented herein exhaust vapor condensation technology and application of vacuum on the rotors of the turbines in thermoelectric plants presents a growing development, but the efficiency of these vacuum condensation equipment is questionable.
Aimed at developing a vacuum condensation system more efficient the inventors developed this invention particularly for applying at thermoelectrics plants which solves some drawbacks caused by currently available systems.